The present invention relates to vibration in mechanical systems and, more particularly, relates to an apparatus and associated method for damping vibration.
Satellites, spacecraft and other payloads are typically transported or launched into orbit using a launch vehicle, such as a rocket. Most payloads are attached to the launch vehicle only at the base of the payload such that the payload is cantilevered to the vehicle. During launch, and while the payload is being transported to its proper orbit and velocity, the payload is subjected to a severe vibration and acoustic environment that creates dynamic loads or vibroacoustic loads (referred to herein as xe2x80x9cvibrationxe2x80x9d) that are transmitted to the payload from the launch vehicle. The vibration can be the result of environmental effects such as wind gusts, as well as events such as motor ignitions and cut-offs, fuel depletion and stage jettisons. The vibration can have large amplitudes over a wide frequency range that can damage a payload and even cause post-orbit malfunctions. Due to the cost associated with the manufacture of most payloads, vibration is considered to be an important factor in the structural design of both payloads and launch vehicles.
Conventional approaches to improving launch survival of payloads have typically involved stiffening the structural components of the payload, as well as the fairing or mount securing the payload to the launch vehicle. However, structural stiffening usually requires the use of exotic and/or expensive materials and can necessitate an undesirable increase in the overall weight of the payload and the launch vehicle. In addition, the stiffened structural components still must undergo extensive and expensive testing to ensure that the payload will have a reasonable probability of launch survival. Other approaches have involved the use of flexible materials to isolate and reduce vibration in the axial direction between the vehicle and payload. However, such approaches typically rely on friction to support shear loads, which can negatively affect the flexibility and integrity of the flexible materials.
Thus, there remains a need to replace the conventional design approach of structural stiffening with a vibration isolator that can securely attach a payload to a vehicle while at the same time effectively damp the transmission of vibration between the vehicle and the payload. The vibration isolator should be capable of damping the transmission of vibration about three axes and of supporting shear loads without relying on friction. In addition, the isolator must be such that it can be manufactured and assembled with a minimum number of parts to reduce the overall weight of the payload and vehicle and so that the isolator can be easily assembled and disassembled, particularly in low-gravity environments.
The present invention provides a vibration isolator that can securely attach a payload to a vehicle, as well as effectively dampen the transmission of vibration between the vehicle and the payload about three axes. The vibration isolator includes a plurality of elastomeric members, which can be formed of silicone, natural and synthetic rubber, or any other elastomer having a relatively high density, modulus of resilience, and modulus of elasticity. The vibration isolator also includes a first support, a second support and at least one third support. The first, second and third supports cooperate with the plurality of elastomeric members to damp vibration between the first and second supports. At least one, and preferably both of the first and second supports have a circular configuration. The at least one third support can be configured in the shape of a plate or have a circular configuration. The first, second, and third supports can be formed of aluminum, AA 2000 series aluminum alloys, AA 7000 series aluminum alloys or titanium.
According to one embodiment, the second support is spaced from the first support such that the first and second supports define at least one recess therebetween. The at least one third support is spaced from the first support such that the first and third supports define at least one recess therebetween. The recesses between the first and second supports and the first and third supports are each structured to at least partially receive at least one of the elastomeric members. According to one embodiment, at least one and, preferably, all three of the first, second and third supports has at least one outer surface defining a plurality of angled surfaces about the perimeter thereof that at least partially define the recesses between the supports and retain the corresponding elastomeric members. Advantageously, the angled surfaces allow the vibration isolator to transmit vibration through the elastomeric members in three axes without excessively restraining the elastomeric members, which would reduce their flexibility. In addition, because the elastomeric members are allowed to bulge within the recesses and, more specifically, against the angled surfaces, the isolator can support shear loads without relying on friction. The vibration isolator includes at least one fastener being structured to mount the at least one elastomeric member between the first support and the at least one third support and mount the at least one elastomeric member between the first support and the second support such that elastomeric members damp vibration transmitted between the first and second supports.
In another embodiment of the present invention, the vibration isolator includes a first support having first and second flanges and a web portion extending therebetween. The vibration isolator includes a second support having first and second flanges and a web portion extending therebetween. The first flange of the second support is spaced from the second flange of the first support so as to define at least one recess therebetween. Each recess is structured to at least partially receive at least one of the elastomeric members. In one embodiment, the second flange of the first support and the first flange of the second support have outer surfaces defining a plurality of angled surfaces about the perimeter thereof adapted to retain a corresponding elastomeric member. The vibration isolator includes at least one third support spaced from the second flange of the first support. The at least one third support and the second flange of the first support define at least one recess therebetween. Each recess is structured to at least partially receive at least one of the elastomeric members. In one embodiment, the at least one third support and the second flange of the first support have outer surfaces defining a plurality of angled surfaces about the perimeter thereof adapted to retain a corresponding elastomeric member. The vibration isolator also includes at least one fastener that is structured to mount a corresponding elastomeric member between the second flange of the first support and the at least one third support and mount a corresponding elastomeric member between the second flange of the first support and the first flange of the second support such that the plurality of elastomeric members damp vibration transmitted between the first support and the second support.
In still another embodiment, the present invention provides a transport system including a payload and a vehicle for transporting the payload. The transport system includes a vibration isolator for damping vibration between the vehicle and the payload. The vibration isolator includes a first support having first and second flanges and a web portion extending therebetween. The first flange of the first support can be secured to the payload using suitable fasteners. The vibration isolator includes a second support having first and second flanges and a web portion extending therebetween. The second flange of the second support can be secured to the vehicle using suitable fasteners. In another embodiment, the first flange of the first support is secured to the vehicle and the second flange of the second support is secured to the payload. The first flange of the second support is spaced from the second flange of the first support so as to define at least one recess therebetween. Each recess is structured to at least partially receive at least one of the elastomeric members. The vibration isolator includes at least one third support spaced from the second flange of the first support. The at least one third support and the second flange of the first support define at least one recess therebetween. Each recess is structured to at least partially receive at least one of the elastomeric members. The vibration isolator includes at least one fastener that is structured to mount a corresponding elastomeric member between the second flange of the first support and the at least one third support and mount a corresponding elastomeric member between the second flange of the first support and the first flange of the second support such that the plurality of elastomeric members damp vibration transmitted between the first support and the second support.
The present invention also provides a method of damping vibration. The method includes providing a first support having at least one outer surface defining a plurality of angled surfaces about the perimeter thereof. A second support is provided having an outer surface spaced from an outer surface of the first support. The outer surface of the second support defines a plurality of angled surfaces about the perimeter thereof. At least one elastomeric member is positioned at least partially between the angled surfaces of the first and second supports. The at least one elastomeric member is preferably secured between the first and second supports. The at least one elastomeric member is displaced against the angled surfaces of the first and second supports to thereby dampen vibration between the first and second supports. In another embodiment, the method further includes providing at least one third support having an outer surface spaced from an outer surface of the first support, the outer surface of the at least one third support defining a plurality of angled surfaces about the perimeter thereof. At least one elastomeric member is positioned at least partially between the angled surfaces of the first and third supports. The at least one elastomeric member is preferably secured between the first and third supports. The at least one elastomeric member is displaced against the angled surfaces of the first and third supports to thereby dampen vibration between the first and second supports.
In another embodiment of the present invention, the method includes attaching a first support to a payload. A second support is attached to a vehicle. At least one elastomeric member is positioned between the first and second supports. At least one third support is positioned adjacent the first support. At least one elastomeric member is positioned between the first and third supports. The first, second and third supports are secured together to thereby mount the corresponding elastomeric members between the first and second supports and between the first and third supports. In one embodiment, the elastomeric members are secured between the corresponding supports by inserting at least one fastener through the first, second and third supports and the elastomeric members positioned therebetween. The elastomeric members positioned between the corresponding supports are displaced to thereby dampen vibration between the vehicle and payload.